Gallstones are more common in women than in men, especially after the age of 40.
Gallstones are hardened deposits of digestive fluid that form in the gallbladder and are made up of several substances, including cholesterol and bilirubin (main bile pigment), which crystalize in much the same way as sugar collecting in the bottom of a syrup jar. Gallstones can vary in size from as tiny as a grain of sand to as large as a golf ball. People may develop just one single stone or hundreds.